Steaming stones

Published: Monday 30 September 1996

Beneath the lofty Himalayan ranges lie extremely hot and radioactive rocks, the origin of which has remained a point of debate among geologists for years now. Recently, Audrey Huerta, a geophysicist at the Massachusetts Institute of Technology in the US, offered yet another explanation. She suggests that these rocks originally came from the surface of the Indian tectonic plate and were thrust 20 to 30 km underneath the emerging mountain range during its collision with the Asian plate. Demonstrating through a computer model, Huerta suggests that once these rocks were in place underneath the mountains, they became insulated and began to build up heat as the collision zone thickened. She says that a unique collection of minerals like uranium, thorium and potassium got eroded from the top of the Asian plate and was buried between the two plates during collision. This mixture of minerals led to an unusual rise in the temperature of these rocks which are twice as hot as the most stable rocks at that depth.

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